The use of fastening or locking means operated by a rotatable knob has been known for some time for many applications, currently mainly in the footwear sector, consisting of a casing that is attached to a first flap of the item to be locked, for example a shoe or boot, a knob with a reel rotatably attached to the casing, at least one cable attached at one end to a reel around which it is wound and at the other end, on the exterior of the casing, to a second flap of the item to be locked.
By way of example, fastening means of this type, specifically concerning the footwear sector, are described in documents EP 1213981 B1 and EP 2789251 A1.
By operating the knob it is possible to rotate the reel which, by winding the cable, causes the two flaps attached to the ends of the cable to move closer together in order to achieve a correct degree of locking.
The rotatable knob is therefore positioned on the exterior of the casing and is designed to cause the rotation of the reel by manual control, to tighten the locking cable. In addition, the knob and the reel can be axially released from each other so that the knob can be moved from a gripping position with the reel to a release position in which the cable is unwound from the reel, releasing the fastening.
Mechanical means, designed to block the reel in the desired position in one rotation direction and designed to release the reel in the opposite direction, are present between the knob and the reel.
These mechanical means consist of gear mechanisms that interact, in the locking step, with the means of constraint, generally the ratchet type, with which the reel is provided, and operate in such a way that the knob can be moved from a lowered gripping position, in which the cable is tautened and locked, and rotated to a raised release position to allow the release and slackening of the cable.
The problem encountered with the use of such devices substantially concerns the fact that in the release step, allowed by raising the knob which frees the reel, the cable unwinds in an uncontrolled and instantaneous way, immediately releasing the previously constrained parts, since the knob is normally constrained to the reel only in the gripping step, while it is completely freed from the reel which becomes idle in the release step with the knob raised.
The uncontrolled opening due to the instantaneous release of the cable when the knob is raised from the gripping position could, in some situations, cause problems, especially in cases in which this type of fastening is used in combination with some particular applications, such as orthoses or braces used in the orthopedic and rehabilitation sector, in which conditions of instantaneous release, starting from a restraining or gripping position, could lead to the immediate detachment of components that should, instead, preferably, and in some cases necessarily, open gradually.
Document US 2007/0084956 A1 discloses a string fastening device including a reel on which a string is reeled thereon and a toothed ring is connected to the reel. A knob has a shaft inserted into a tube extending from the base of the device and the reel is rotatably mounted on the tube. The knob has first teeth in an underside thereof and the first teeth are engaged with the toothed ring so that the reel is driven by rotation of the knob to tighten the ring. The knob can be pulled away from the reel to disengage the first teeth from the toothed ring so that the string can be loosened. The knob includes second teeth and the base has two pawls which limit the knob to rotate in one direction to drive the reel.